Maheshwar M M, Cheadle J P, Jones A C, Myring J, Fryer A E, Harris P C, Sampson J R
Institute of Medical Genetics, University of Wales College of Medicine, Cardiff, UK.
Hum Mol Genet. 1997 Oct;6(11):1991-6. doi: 10.1093/hmg/6.11.1991.
Tuberous sclerosis is an autosomal dominant trait in which the dysregulation of cellular proliferation and differentiation results in the development of hamartomatous growths in many organs. The TSC2 gene is one of two genes determining tuberous sclerosis. Inactivating germline mutations of TSC2 in patients with tuberous sclerosis and somatic loss of heterozygosity at the TSC2 locus in the associated hamartomas indicate that TSC2 functions as a tumour suppressor gene and that loss of function is critical to expression of the tuberous sclerosis phenotype. The TSC2 product, tuberin, has a region of homology with the GTPase activating protein rap1GAP and stimulates the GTPase activity of rap1a and rab5a in vitro. Here we show that the region of homology between tuberin and human rap1GAP and the murine GAP mSpa1 is more extensive than previously reported and spans approximately 160 amino acid residues encoded within exons 34-38 of the TSC2 gene. Single strand conformation polymorphism analysis of these exons in 173 unrelated patients with tuberous sclerosis and direct sequencing of variant conformers together with study of additional family members enabled characterisation of disease associated mutations in 14 cases. Missense mutations, which occurred in exons 36, 37 and 38 were identified in eight cases, four of whom shared the same recurrent change P1675L. Each of the five different missense mutations identified was shown to occur de novo in at least one sporadic case of tuberous sclerosis. The high proportion of missense mutations detected in the region of the TSC2 gene encoding the GAP-related domain supports its key role in the regulation of cellular growth.
结节性硬化症是一种常染色体显性性状，其中细胞增殖和分化的失调导致许多器官中错构瘤性生长的发展。TSC2基因是决定结节性硬化症的两个基因之一。结节性硬化症患者中TSC2的种系失活突变以及相关错构瘤中TSC2位点的杂合性体细胞缺失表明，TSC2作为一种肿瘤抑制基因发挥作用，其功能丧失对于结节性硬化症表型的表达至关重要。TSC2产物tuberin与GTP酶激活蛋白rap1GAP有一个同源区域，并在体外刺激rap1a和rab5a的GTP酶活性。我们在此表明，tuberin与人类rap1GAP和小鼠GAP mSpa1之间的同源区域比以前报道的更广泛，跨越TSC2基因外显子34 - 38内编码的约160个氨基酸残基。对173名无关的结节性硬化症患者中这些外显子进行单链构象多态性分析，并对变异构象体进行直接测序，同时对其他家庭成员进行研究，从而在14例病例中确定了与疾病相关的突变。在8例病例中鉴定出发生在外显子36、37和38中的错义突变，其中4例具有相同的复发性变化P1675L。所鉴定的5种不同错义突变中的每一种在至少1例散发性结节性硬化症病例中均显示为新发突变。在编码GAP相关结构域的TSC2基因区域中检测到的错义突变比例很高，这支持了其在细胞生长调节中的关键作用。
